1. Field of the Invention
The present invention relates to a reciprocating apparatus and a printer including the reciprocating apparatus.
2. Discussion of Related Art
There is known an image recording apparatus which records an image on a recording medium by ejecting ink to the recording medium based on an input signal, in particular, by introducing the ink to a recording head including an actuator such as a piezoelectric element, an electrostriction element and a heating element, so as to give pressure the ink to eject by utilizing a deformation of the piezoelectric element or the electrostriction element based on the input signal or a partial boiling of the ink by the heating element.
For example, the image recording apparatus called a “serial printer” includes the recording head carried by a carriage which is reciprocateable in a direction perpendicular to a direction of feeding a recording sheet as a recording medium (a sheet-feed direction). The recording head is reciprocated together with the carriage after each time the recording sheet is fed by an amount corresponding to a line feed amount, and ejects the ink to the recording sheet so as to form an image on the recording sheet. The carriage is reciprocated by a drive force applied from a carriage drive device including a belt drive mechanism. A resolution of the image recording by the image recording apparatus is, for example, approximately from 300 dpi to 2400 dpi, so the reciprocating movement of the carriage should be controlled with high accuracy. As one example of the control of the carriage, Patent Document 1 (JP-A-11-132788) discloses that the carriage is controlled based on a position of the carriage detected by a linear encoder as a kind of a carriage movement detector. The linear encoder is arranged to output a pulse signal when sensible portions of an encoder strip thereof are sensed by an optical sensor fixed to the carriage.
As disclosed in Patent Document 2 (JP-A-2004-230802), there are provided a guide shaft and a guide rail as guide members to support the above-described carriage and to guide the carriage. For example, in a case in which the guide shaft and the guide rail formed in a pair to guide the carriage, the guide shaft and the guide rail can be arranged to align in two ways: vertically and horizontally. In a case in which the guide shaft and the guide rail are arranged to align horizontally, the image recording apparatus can be reduced in size and in thickness. On the other hand, the carriage can be easily rotated about an axis parallel to a vertical direction, causing the recorded image to be poor in quality or defective.
As disclosed in Patent Document 3 (JP-A-2001-121721), when the above-mentioned recording head ejects ink, a part of the ejected ink becomes a tiny mist-like ink (hereinafter referred to as a “ink mist”) and floats in a space in the image recording apparatus. The ink mist sticks to the encoder strip of the linear encoder and thereby influences the sensing of the sensible portions by the optical sensor, causing to lower the accuracy of a position detection of the carriage by the linear encoder.
When a pair of guide rails aligned horizontally support the carriage and guide a reciprocating movement of the carriage, there is a tendency that the carriage is rotated about the axis parallel to the vertical direction on the guide rails. Therefore, for improving the accuracy of the position detection, it is desirable that the encoder strip of the linear encoder is disposed at a position where is free of the influence of the above-mentioned rotation of the carriage.
Also, there is provided a guide portion on one of the pair of guide rails so as to define a position of the carriage in a direction perpendicular to the direction of reciprocating movement of the carriage. The carriage has slide surfaces for reciprocating on upper surfaces (slide surfaces) of the guide rails and on the guide portion. A lubricant such as grease is spread on the slide surfaces such that the carriage reciprocates smoothly. For example, during an operation for recovering from a trouble such as paper jam, an operator may contact the encoder strip, thereby the encoder strip is bent. Accordingly, the encoder strip contacts the slide surfaces of the guide rails and the guide portion, causing that the lubricant on the slide surfaces is stuck to the encoder strip. Some lubricant is transparent, but dust is easily stuck to the lubricant because of its viscosity. The encoder strip becomes dirty with the dust stuck thereto via the lubricant, causing the sensible portions (of the encoder strip) to be undetectable by the optical sensor, and accordingly lower the accuracy of the position detection of the carriage.
There is one example of a recording head which is carried by the carriage and which supplies ink via an ink tube from an ink cartridge. The ink tube has a length so as to follow the reciprocating movement of the carriage without preventing said movement of the carriage. The ink tube is bent in a generally U-shape in a space between the carriage and a main body of the image recording apparatus. The ink tube has a flexibility enabling the U-shape of the ink tube to be changed by the reciprocating movement of the carriage, so as to follow the movement of the carriage. At the time, the ink tube is shaken so as to contact the slide surfaces of the guide rails, the guide portion and the encoder strip, so that the lubricant applied on the guide rails could be stuck to the encoder strip, possibly reducing the accuracy in detecting the position of the carriage.